If you use henna to dye your hair or create henna tattoos, you may have found yourself throwing away leftover paste. However, it is possible to freeze leftover henna and use it later. If your henna is stored properly in an airtight freezer bag, it will keep for months. Once the henna has returned to room temperature, you can scoop it into a mehndi cone to make tattoos or work it through your hair to achieve a rich red dye.
Remove the frozen henna paste from the freezer. Place the bag of henna in a plastic bowl and set the bowl on the counter. Wait several hours for the henna to return to room temperature before using it.
Fill a plastic bowl with very hot (but not boiling) water. Put the sealed freezer bag containing the henna into the bowl of water. The henna will be ready to use within half an hour.
Place the freezer bag in the refrigerator if you don't need to use the henna until the next day. Leave the bag in the refrigerator overnight. Remove the thawed henna from the refrigerator the following day and allow it to reach room temperature before you use it.
Stir a small amount of warm water into the thawed henna if it feels too thick to use. Add the water one spoonful at a time, stirring between spoonfuls, until the henna reaches the desired consistency.